Evolution of the structural and electronic properties of beryllium-doped aluminum clusters: comparison with neutral and cationic aluminum clusters

Abstract

The lowest-energy structures of the Al_nBe (n = 1–13) clusters are obtained and compared with the corresponding Al_n+1 and Al_n+1⁺ (n = 2–13) as well as Al_nMg clusters at the B3LYP/aug-cc-pVDZ level. The configurations of Al_nBe show strong resemblances to those of pure Al_n+1 clusters, and the first three-dimensional ground state in the Al_nBe clusters occurs for Al₃Be. Various properties of the Al_nBe clusters are systematically investigated using the CCSD(T) method and their thermodynamic properties are also compared with those of corresponding Al_n+1⁺ clusters. The evolution of the energetic and electronic properties with the size of the clusters shows the unique stability of the 20-valence electron systems Al₆Be and Al₇⁺, which can be understood from the spherical jellium model (SJM). However, different from Al₇⁺ with 1s²1p⁶1d¹⁰2s² shell occupation, the electronic-shell structure of 1s²1p⁶1d⁶2s²1d⁴ for the Al₆Be cluster demonstrates that the impurity atom makes the molecular orbital distribution of doped clusters much more complex than that of pure metal clusters.